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On March 1, 2001, at 0821, Unit 2 was oper … On March 1, 2001, at 0821, Unit 2 was operating at 95% power, activities were underway to remove the 345kV switchyard North Bus for maintenance. Switchyard breaker Y590 was opened. Unknown to the operating crew, the C phase pole of switchyard breaker Y600 which had been previously closed, remained opened. With the C phase pole of breaker Y600 still opened, the Control Room received electrical panel alarms and the three operating Circulating Water Pumps tripped offline, requiring the operating crew to initiate a manual reactor trip in accordance with plant procedures.</br></br>All control rods fully inserted. All actuated safety equipment operated as required. The root cause identified for this event is failure of the operating linkage of switchyard breaker Y600 C phase pole. The bushing required between the linkage pin and the operating linkage was not installed and most likely left out during fabrication. Corrective actions include repair of the failed breaker, inspection of a similar switchyard breaker, and further review of switchyard breaker inspection procedures.</br></br>This event was reviewed for risk impact and found to be risk insignificant since the conditional core damage probability is less than 2x10-7.re damage probability is less than 2x10-7. +
On March 1, 2001, at 0821, Unit 2 was oper … On March 1, 2001, at 0821, Unit 2 was operating at 95% power, activities were underway to remove the 345kV switchyard North Bus for maintenance. Switchyard breaker Y590 was opened. Unknown to the operating crew, the C phase pole of switchyard breaker Y600 which had been previously closed, remained opened. With the C phase pole of breaker Y600 still opened, the Control Room received electrical panel alarms and the three operating Circulating Water Pumps tripped offline, requiring the operating crew to initiate a manual reactor trip in accordance with plant procedures.</br></br>All control rods fully inserted. All actuated safety equipment operated as required. The root cause identified for this event is failure of the operating linkage of switchyard breaker Y600 C phase pole. The bushing required between the linkage pin and the operating linkage was not installed and most likely left out during fabrication. Corrective actions include repair of the failed breaker, inspection of a similar switchyard breaker, and further review of switchyard breaker inspection procedures.</br></br>This event was reviewed for risk impact and found to be risk insignificant since the conditional core damage probability is less than 2x10-7.re damage probability is less than 2x10-7. +
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